TheClimateChanger

Today will be the 9th consecutive day without measurable rainfall at the airport, assuming nothing pops up (there were a few scattered showers earlier north). Only 0.39" over the past 21 days.

Interesting temperature pattern yesterday in the northeast. Map below shows yesterday's high temperature percentile. Much of the interior decidedly above the median high temperature - generally 70 to 85 percentile. Buffalo was only a few degrees shy of a record, topping out at 89F as an odd easterly flow brought some downsloping sending the warmest temperatures to the lakeshore (typically cooler locations). The coastal Plain was pretty close to the median - generally from about the 33rd to 67th percentile, except for Boston, which didn't make it out of the low 70s. The ASOS at Logan is very close to the water. Big divergence from BOS to Blue Hill Observatory (Milton, Mass.) just to the south. Cooler high temperatures in West Virginia from clouds and showers.

Summer ain't over yet!

Today's thread:

In a stunning departure from the conditions of the summer to date, August has started off on a very cool note nationwide. The PRISM data below is only for the first two days of the month, but yesterday saw similarly impressive cold with a number of record low max temperatures in the south and a few isolated record lows in the eastern US. While I still expect August to finish out above normal for CONUS, this is going to make a new summer national record quite difficult. Will probably take a few days just to return to 1991-2020 means nationally, which means we are likely looking at one of the coolest first weeks of August in a long while. Probably would need an epic heat wave to keep pace with 2021 & 1936, at this point.

Beautiful stretch. At PIT, we've doubled our July tally of low temperatures below 60F in the first four days of the month. Happy I've been able to give the A/C a rest for a change.

Wow, I don't agree with this statement at all. Recent Julys have had mean minimum temperatures that are warmer than the mean 24-hour averages from past "cold" Julys. Probably after 2050, we will begin to see Julys where the mean minimum temperatures exceed the mean maximum temperatures from old-school cold Julys. For some reason, you only ever look and compare to the hottest years? For example, JFK's mean minimum last month was 72.7F. That exceeds the mean 24-hour average of 71.8F in 1956, 72.2F in 1996, 72.2F in 1965, 72.3F in 2000, 72.4F in 2001, and falls just shy of the 72.8F observed in 1976. It's probably just a handful of decades before JFK starts seeing low temperatures in July that exceed the mean maximum temperatures observed in cold Julys (e.g., 1956, 77.9F; 1996, 78.6F; 2000, 79.5F; and 1967, 79.7F). I don't think its too hard to imagine a future in 2060 where NYC looks more like Washington, DC of 2000-2020, where such low temperatures are common. I think it's significant when low temperatures are exceeding the mean of high and low from many past years. In the first 6 years after installation of the ASOS at JFK, there were 3 years in which the month of July had a colder mean temperature than this year's mean low temperature (1996, 2000, and 2001).

"It's only summer." Just kidding. Actually, the weather today and this weekend is closer to "only summer" weather than the past 6 weeks. The mean minimum temperature of 68.2F at PIT last month was 0.8F higher than the mean average (avg. of max & min) temperature from 1976, and pretty comparable to the mean average temperature observed in 1960, 1984 & 2000.

You can even see the point where atmospheric changes start to swamp out the UHI signal. From 1970-2000, both sites show a small cooling trend, with NYC lows dropping 0.2F, while the Charlotteburg site saw lows drop by 0.7F during that timeframe. Hard to tell if the late 20th century cooling is a real trend or just an artifact from changing equipment/observation practices and site location. I'm not sure if that cooling trend is real or just manufactured by those non-climatic factors.

Wow, since 1970, July nighttime low temperatures at NYC have risen 3.1F, while lows at Charlotteburg Reservoir have risen 7.1F, per linear regression.

I mean not every month is just going to continue being cooler than the corresponding month in 2024. Eventually that trend has to stop, no? Maybe in time for December, which was about a degree cooler than normal in 2024.

Last year was record warm only for the period 1869-2024. For the period 2025+, it will be considered a cool year.

2007 also had crazy heat in the south and Ohio Valley. I don't think summer is over yet.

Analogs seem good for some big heat. I see 1953, a couple from 1988, 2001 (big heat in early August), 2002.

That rubber band is going to snap in a BIG way soon, I would imagine.

Good post, Tip. I expect Massachusetts to finish around 73.7F for the month (+/- 0.3F). Very crowded field. That figure would place them in ninth, but just an extra tenth would move 2025 instead to a 4-way tie for 6th. There seems to have been a reversal from the era of the 2010s where ASOS sites like Logan often ranked higher than state-wide averages. Now, the warmth is being driven more by coop sites. Blue Hill Observatory in Milton, Mass. notched is 4th hottest July on record. Looks like maybe there's been some amelioration of the urban heat island effect, perhaps by having created a more effective atmospheric blanket over the smaller towns and rural locations, thereby negating the conditions that drove the unbelievable radiational conditions some of these areas used to experience?

This is an interesting map. Number of 90+ days since June 1. All the long-term climate stations along the I-95 are in the top 10, except for NYC, which is tied for 44th. Things that make you go hmmm...

Definitely showing up in the observations with visibility down to 2 1/2 miles.

I would say it is. I asked xAI's Grok to estimate what the climate of New York City would have looked like at the height of the last glacial maximum. I think most here would agree that this is MILES better than the current climate. Month Estimated Mean Temperature (°C) Estimated Mean Temperature (°F) January -15 to -10°C 5 to 14°F February -14 to -9°C 7 to 16°F March -10 to -5°C 14 to 23°F April -3 to 2°C 27 to 36°F May 3 to 8°C 37 to 46°F June 10 to 15°C 50 to 59°F July 12 to 17°C 54 to 63°F August 10 to 15°C 50 to 59°F September 5 to 10°C 41 to 50°F October 0 to 5°C 32 to 41°F November -5 to 0°C 23 to 32°F December -12 to -7°C 10 to 19°F Winter (Dec–Feb): Very cold, with means likely between -15°C and -7°C (5–19°F), similar to modern subarctic or high-latitude tundra climates. Frequent snow was probable, but low precipitation meant less accumulation than in modern snowy regions like upstate New York. Summer (Jun–Aug): Short and cool, with July means likely 12–17°C (54–63°F), resembling modern high-latitude coastal areas (e.g., parts of Iceland or northern Canada). Proximity to the ice sheet and cold Atlantic Ocean currents kept summers chilly. Precipitation and Snow: The climate was drier than today due to cold air holding less moisture. Snow was common in winter, but total accumulation was likely moderate, with a tundra-like landscape. Permafrost was widespread, affecting soil and vegetation. Ice Sheet Influence: The Laurentide Ice Sheet, terminating near Long Island, would have cooled NYC via cold air drainage and albedo effects. Cold ocean currents along the Atlantic coast further suppressed temperatures. Variability: Daily and annual variability was likely high, with cold snaps in winter and occasional warm days in summer. Strong winds from the ice sheet (katabatic winds) could have made conditions feel even colder.

I don't think one night in the upper 30s would do much harm to corn/maize. Obviously, if it was consistently cold (and/or moist) that would affect growth. Consistently warm overnight temperatures are a bigger concern because the plant can respire through the night and burn stored energy faster than it can be replenished. Corn is native to higher latitudes in Mexico. It does best with overnight lows from in the 50s/low 60s.

Daily Data for July 3, 1929 for New Jersey Click column heading to sort ascending, click again to sort descending. LAYTON 3 NW COOP 72 33 RUNYON COOP 76 37 CHARLOTTEBURG RESERVOIR COOP 71 38 SUSSEX 1 NW COOP 73 40 HIGHTSTOWN 2 W COOP 75 42 SOMERVILLE 4 NW COOP 75 42 BELLEPLAIN STA FOREST COOP 76 43 INDIAN MILLS 2 W COOP 76 43 PLAINFIELD COOP 76 44 BELVIDERE COOP 77 44 LITTLE FALLS COOP 75 44 Belvidere Area ThreadEx 77 44 DOVER COOP 73 44 PLEASANTVILLE 1 N COOP 80 45 TUCKERTON 2 NE COOP 80 45 BOONTON 1 SE COOP 76 45 ROEBLING COOP 80 46 FLEMINGTON 5 NNW COOP 76 46 MOORESTOWN 4 E COOP 75 47 PHILLIPSBURG COOP 75 47 RIDGEFIELD COOP 75 47 CULVERS LAKE COOP M 47 LAMBERTVILLE RIVER COOP 73 47 LONG BRANCH-OAKHURST COOP 76 48 NEW BRUNSWICK EXPERIMENT STATION COOP 74 48 NEW MILFORD COOP 78 48 NEWTON COOP 78 48 New Brunswick Area ThreadEx 74 48 TRENTON-NOTTINGHAMWA COOP M 50 PATERSON COOP 76 51 TRENTON WBAN 73 53 Trenton Area ThreadEx 73 53 CAPE MAY 2 NW COOP 76 54 JERSEY CITY COOP 79 56 ATLANTIC CITY MARINA WBAN 78 58 Atlantic City Marina Area ThreadEx 78 58 ELIZABETH COOP 78 70

According to the records of NCEI, lows in the 30s were observed somewhere in the State of New Jersey in the following years. Note, this is not an exhaustive list of ALL 30s. Some of these years had more than one site and/or more than one day in the 30s. This is just the lowest observation each year. The all-time statewide monthly record low is 33F, set at Layton 3 NW on July 3, 1929. The last time a low below 40F was observed in the state during the month of July was July 9, 2000, when Lambertville reported a low of 38F. 1890: 39F 1898: 38F 1899: 38F 1903: 38F 1909: 39F 1912: 36F 1918: 39F 1925: 39F 1927: 36F 1929: 33F 1939: 38F 1943: 39F 1945: 36F 1954: 39F 1957: 38F 1975: 39F 1986: 39F 2000: 38F

For Connecticut, I expect the July mean to come in around 75.2F, which would make this the third hottest July on record. 2023 is tied for 7th hottest with 1999 (mean of 74.8F), and this July has averaged 0.435F warmer across the same basket of stations. Cooler weather today may impact this a bit, but probably at least 75F, which would still be 4th hottest.

Here's what PRISM has for nationwide lows. We have a very good shot at setting a national monthly record here. Current record is around +1.8F (relative to 1991-2020).